Interior lighting systems for automotive and other vehicle applications are generally used for two purposes. One is to provide general area illumination and the other is feature lighting of specific objects, either for aesthetic or functional reasons. Traditionally, these interior lighting systems have utilized incandescent lamps for both area and feature lighting, often using lenses to control the shape and light intensity distribution of the emitted light. Although incandescent lamp systems can often be integrated into various vehicle interior trim components in a simple manner, various considerations do arise which complicates their use for automotive lighting. For example, where heat from the lamp could damage adjacent components or otherwise cause problems, thermal management of that heat must be implemented. Also, there is often little room in or behind a particular vehicle interior body panel or trim component for the lamp, socket, and lensing.
This constraint on space behind the vehicle panels can be especially true with vehicle headliners where there may be little room between the headliner and roof of the vehicle. For headliners, the solution has typically been to either require more room between the headliner and roof or to utilize a light assembly that protrudes downwardly from the headliner for a short distance. Where sufficient space is available, various functional components such as electrical conduits, lamp soffits, electrical connectors, HVAC ducts, flat speakers, and head airbags can be molded into the headliner during its manufacture. See, for example, European Patent Application EP 0979760, published Feb. 16, 2000. However, where the headliner thickness is to be kept to a minimum, the use of molded-in lamp soffits may not be practical.
The use of alternative light sources, such as electroluminescent panels, has been proposed for a wide range of vehicle lighting applications. For example, U.S. Pat. No. 4,864,473 to Tokarz et al. discloses an electroluminescent panel dome lamp designed for a convertible-type automobile. The panel is mounted on a housing that is attached to the headliner of the convertible's roof. U.S. Pat. No. 5,013,967 to Hirotaka et al. discloses a detachable electroluminescent panel light source that can be located at various places about the inside of a vehicle to provide illumination. These locations include inside the trunk, at the glove compartment, and on the backside of the front seats. U.S. Pat. No. 5,564,813 to Curtindale discloses a sun visor that includes incandescent light sources to provide courtesy, reading, and vanity illumination. The patent states that electroluminescent lighting strips could be used in place of the incandescent lamps. However, while various automotive lighting uses of electroluminescent panels have been proposed, as exemplified by these patents, much of the prior art discloses the use of electroluminescent panels as a direct substitute for incandescent and/or LED lamps without taking full advantage of the unique structural features of the electroluminescent technology.
Accordingly, it is a general object of the invention to provide a vehicle interior lighting system that can be used to provide area or feature fighting in a manner that minimizes the aesthetic impact of the light source when not in use and that requires negligible space behind the interior body panel or trim component where the light source is located.